From: [EMAIL PROTECTED] Date: Tue, 19 Apr 2005 15:14:19 EDT
Ive done LOTS of research. First of all, the DayStar 80MHz PowerPro has 4 72 pin slots on it, so I will definitely get at least 384MB RAM total, maybe 512 if the 64MBs will work on the PowerPro.
Ah, I missed the detail that you're looking at the PPC upgrade with RAM slots on board. I had forgotten that that beast existed. Mea Culpa.
Second, I know that by just
increasing the bus speed on the PowerPro, and thus the processor, it wont go faster
than 85 or 90MHz. Third, I know a 100MHz 601 can make it to or almost to
120MHz.
According to IBM, the 100 MHz 601 will get to 120 MHz with cooling. That usually means installing a Peltier Thermoelectric cooler, which you will find on the various PPC601 Macs and clones built to run 100 MHz or faster.
The difficulty with overclocking the bus speed may not be in the CPU, though. It could be that the PowerPro will not sync up with the motherboard if its (the upgrade card's bus) speed is outside a certain range. Your mention that it won't run unless the host motherboard is running at 25 or 33 MHz would seem to support this hypothesis.
My experience with the Turbo601 (also designed by Daystar and probably quite similar in technology) was that the card would only operate in a very narrow range of frequencies. Before modifying it to clock triple, I found that it would only operated from about 29 MHz to 34 MHz, which yielded CPU speeds of 58 MHz to 68 MHz. So I knew the problem was not in the CPU speed tolerance, but in the card clock synchronization.
The PowerPro may be similar. You should try adjusting the clock speed of the unmodified card *downwards* and see how much tolerance it has. This will give you a better feel for whether a clock tripling modification will work.
Certainly, you cannot get the existing CPU chip to run at 120 MHz. So, if you did a clock tripling modification, and left the bus speed at 40 MHz, it would not work. However, you might be able to do a clock tripling modification and get 96 - 100 MHz out of it, if it will tolerate running at 32 - 33 MHz.
Once you have a clock tripling modification working, then it would be time to look at replacing the CPU chip. If you do all the modifications at once, and it doesn't work, troubleshooting will be a bear. Of course, you could try replacing the CPU first without modifying the clock speed and see if you can get the replacement CPU chip to work.
There was also an "Unofficial Home Page" for the PowerPro, I believe. I know there was one for the Turbo601 and I believe it had a link to the one for the PowerPro. That might be an avenue that could lead to high resolution scans of the card.
Jeff Walther
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